Propylene catalysts, rhodium complexes

To make butyraldehyde, the precursor for NBA, the so-called Oxo process is used, reacting chemical grade propylene with hydrogen and. carbon monoxide at 250-300°F and 3500-4000 psi. See Figure 14-4.) Under those conditions, both feeds are liquids. The catalyst is an oil-soluble cobalt carbonyl complex dissolved in the propylene. If rhodium-based catalysts or complexes based on rhodium carbonyls and triphenyl phosphine... 

Copper compounds are catalysts for the Michael addition reaction (249), olefin dimerizations (245, 248), the polymerization of propylene sulfide (142), and the preparation of straight-chain poly phenol ethers by oxidation of 2,6-dimethylphenol in the presence of ethyl- or phenyl-copper (209a). Pentafluorophenylcopper tetramer is an intriguing catalyst for the rearrangement of highly strained polycyclic molecules (116). The copper compound promotes the cleavage of different bonds in 1,2,2-tri-methylbicyclo[1.1.0]butane compared to ruthenium or rhodium complexes. Methylcopper also catalyzes the decomposition of tetramethyllead in alcohol solution (78, 81). 

Chemistry. The hydroformylation of allyl alcohol is illustrated in Eq. (58). The catalyst is a rhodium complex modified with triphenylphos-phine of the same type used for production of n-butyraldehyde from propylene in the oxo process. The reaction takes place in a toluene solution at approximately 2-3 atm pressure (15-30 psig) and 60°C (140 F). The conversion to 4-hydroxybutyraldehyde is 98% based on allyl alcohol with a selectivity of 79.1%. 

An example of a large scale application of the aqueous biphasic concept is the Ruhrchemie/Rhone-Poulenc process for the hydroformylation of propylene to n-butanal (Eqn. (15)), which employs a water-soluble rhodium(I) complex of trisulphonated triphenylphosphine (tppts) as the catalyst (Cornils and Wiebus, 1996). 

For instance, catalysis in liquid/liquid two phases is generally referred to as biphasic catalysis and has widened the practical scope of homogeneous catalysis the catalyst is present in one liquid phase, while reactants and products are present in the other liquid phase. Thus, the catalyst can be separated by simple phase separation. Celanese is operating a 300 000 t/a plant for propylene hydroformylation using a water-soluble rhodium phosphine complex in a biphasic mode of operation at the Ruhrchemie site in Oberhausen [142],... 

In most cases the catalytically active metal complex moiety is attached to a polymer carrying tertiary phosphine units. Such phosphinated polymers can be prepared from well-known water soluble polymers such as poly(ethyleneimine), poly(acryhc acid) [90,91] or polyethers [92] (see also Chapter 2). The solubility of these catalysts is often pH-dependent [90,91,93] so they can be separated from the reaction mixture by proper manipulation of the pH. Some polymers, such as the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymers, have inverse temperature dependent solubihty in water and retain this property after functionahzation with PPh2 and subsequent complexation with rhodium(I). The effect of temperature was demonstrated in the hydrogenation of aqueous allyl alcohol, which proceeded rapidly at 0 °C but stopped completely at 40 °C at which temperature the catalyst precipitated hydrogenation resumed by coohng the solution to 0 °C [92]. Such smart catalysts may have special value in regulating the rate of strongly exothermic catalytic reactions. 

The first fixed-bed application of a supported ionic liquid-phase catalyst was hydroformylation of propylene, with the reactants concentrated in the gas phase (265). The catalyst was a rhodium-sulfoxantphos complex in two ionic liquids on a silica support. The supported ionic liquid phase catalysts were conveniently prepared by impregnation of a silica gel with Rh(acac)(CO) and ligands in a mixture of methanol and ionic liquids, [BMIMJPFg and [BMIM][h-C8Hi70S03], under an argon atmosphere. 

For cis-chelate complexes of rhodium and bisphosphines as catalysts, indeed relatively low ratios of n/i aldehyde products were reported (12, 13). Using a 1 1 mixture of H CO at atmospheric pressure, Sanger reported n/i ratios ranging from 3 to 4 for propylene hydroformylation (12). However, his catalyst systems were produced by adding less than 2 mol of bisphosphine per mole tris(triphenyl-phosphine)rhodium carbonyl hydride. When an excess of the chelating bisphosphines was used by Pittman and Hirao (13), low n/i ratios close to 1 were produced from 1-pentene using a mixture of H2/CO at 100-800 psi between 60° and 120°C. 

Description The process reacts propylene with a 1 1 syngas at low pressure (<20 kg/cm2g) in the presence of a rhodium catalyst complexed with a ligand (1). Depending on the desired selectivity, the oxonation reaction produces normal and iso-butyraldehyde with typical n/i ratios of either 10 1 or >22 1. Several different ligand systems are commercially available which can produce selectivity ratios of up to 30 1 and as low as 2 1. The butyraldehyde product is removed from the catalyst solution (2) and purified by distillation (3). N-butyraldehyde is separated from the iso (4). 

Rhodium and ruthenium complexes of CHIRAPHOS are also useful for the asymmetric hydrogenation of p-keto esters. Dynamic kinetic resolution of racemic 2-acylamino-3-oxobutyrates was performed by hydrogenation using ((5,5)-CHIRAPHOS)RuBr2 (eq 3). The product yields and enantiomeric excesses were dependent upon solvent, ligand, and the ratio of substrate to catalyst. Under optimum conditions a 97 3 mixture of syn and anti p-hydroxy esters was formed, which was converted to o-threonine (85% ee) and D-allothreonine (99% ee) by hydrolysis and reaction with propylene oxide. 

The hydroformylation of alkenes is commonly run using soluble metal carbonyl complexes as catalysts but there are some reports of heterogeneously catalyzed reactions of olefins with hydrogen and carbon monoxide. Almost all of these are vapor phase reactions of ethylene or propylene with hydrogen and carbon monoxide catalyzed by rhodium, " 20 ruthenium,nickel, 22,123 cobalt, 23,124 and cobalt-molybdenum 23 catalysts as well as various sulfided metal catalysts. 23,125,126... 

Hydroformylation refers to the addition of hydrogen and carbon monoxide to unsaturated systems. The hydroformylation of olefins is also known as the oxo synthesis or the Roelen reaction in honor of its inventor. It is one of the major industrial processes. Technical plants use cobalt- or rhodium-based catalysts the active species are supposed to be mononuclear complexes (194). The most desired oxo product is butanal, generated by the hydroformylation of propylene (195). 

It has been known for many years that transition metals catalyze reactions of coordinated phosphines (2). Known reactions of phosphines as ligands include carbon-hydrogen lx)nd cleavage (cyclometalation), as well as direct carbon-phosphorus bond cleavage. Such metal-catalyzed reactions of phosphines lead to formation of new metal complexes which can affect catalyst properties. A known example is the reaction of triphenylphosphine to propyldiphenylphosphine during the rhodium-catalyzed propylene hydrogenation or hydroformylation (5). 

Dehydrogenation to methyl methacrylate of the isobotyrate produced by the carbonyiation of propylene in the presence of methanol and a complex of rhodium, cobalt or palladium. The isobutyrate is converted with catalysts based on molybdenum, tungsten, vanadium, phosphomoiybdic acids and possibly heteropolyacids. It has been developed chiefly by Asahi, BASF, Eastman, Mitsubishi, Mobil, foray, etc. 

As water is immiscible with most organic substrates, most reactions involving water are done with liquid-liquid biphasic systems. The use of biphasic organometallic catalysts to catalyze aqueous-phase reactions is a novel method to address this issue. The catalyst in such reactions is a water-soluble transition metal complex with substrates that are partially water-soluble. The Ruhrchemie-Rhone-Poulenc process, which involves hydrofor-mylation of propylene to n-butanol, is an example of biphasic organometallic catalysts being used on an industrial scale (Comils and Kuntz, 1995). The catalyst employed is a water-soluble Rhodium (I) complex of trisulfonated triphenylphosphine (tppts) (see Fig. 5.3). 

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